A. Field of Invention
This invention relates broadly to an improved permanent hair waving or curling process and the composition used therein.
B. Prior Art
Among the components of hair is a proteinaceous material called "keratin". The hair's keratin is made up of long fibrous polypeptide chains which are bonded together with horizontal cross bonds of two forms: hydrogen bonds and cystine bonds, also sometimes referred to as disulfide bonds.
Cystine bonds play an essential role in determining the degree of curl in hair. Some researches in the field believe that straight or slightly wavy hair has relatively fewer cystine bonds and relies heavily upon hydrogen bonding to produce curl or waves in the hair and that very curly hair has a relatively larger amount of cystine bonds. Other researchers in the field believe that straight hair and curly hair may have the same number of cystine bonds, but that the cystine bonds present in straight hair tend to occur in a relatively straight alignment, whereas the cystine bonds present in curly hair tend to occur out of alignment. Regardless of which theory is accepted, while the hydrogen bonds can be broken merely by wetting the hair, such that straight or slightly wavy hair will lose virtually all body when wet, very curly hair maintains its body even when wet because the cystine bonds are relatively unaffected by water. Thus, very curly hair cannot be easily reset into new or different hair styles different from its natural state merely by wetting and shaping the hair.
Permanent hair waving is usually carried out by subjecting the hair to a strong reducing agent, such as hydroxide or, more commonly, materials containing a free "--SH" group or thiol. These "thiol" materials are also called mercaptans. In this treatment, the hair is saturated with the thiol agent, which then acts to break the disulfide bonds.
When a sufficient number of hair disulfide bonds have been broken, the hair is rinsed, removing the unreacted thiol waving agent and disulfide reaction product. The hair is then realigned, e.g., usually by winding on rollers, in order to physically align previously unpaired hair protein thiol groups, i.e., one-half of the cystine groups. The hair and rollers are then saturated with an oxidizing agent, or neutralizer, such as hydrogen peroxide or a bromate salt, to reform disulfide bonds between the newly paired hair protein thiols and to give the hair a configuration or wave. This general process may be used to either add curl or straighten the hair.
Salts of thioglycolic acid, such as ammonium thioglycolate, and thioglycolic acid esters, such as glycerol mono thioglycolate, are typically utilized as the thiol waving agent. Other thiol-containing reagents such as thiolactic acid, beta-mercaptopropionic acid, beta-mercaptobutyric acid, mercaptosuccinic acid and alike have been suggested in the art to be effective.
Prior art waving processes are plagued with the problem of either underwaving or overwaving (under or over processing) that occurs during waving on different parts of a single hair fiber or different areas of the hair mass due to the physical or chemical condition of the hair itself. For example, hair which has been waved, or bleached, or both is more porous than hair which has not undergone these chemical treatments, e.g., these portions of the hair fiber near the hair root which has grown out since the last bleaching or waving. Similarly, even hair having no previous history of bleaching or waving is more porous near the tip end than near the root end simply because hair near the tip has been brushed more, or has been subjected to more weathering.
As a consequence of these porosity differences, the hair tends to take up more waving agent in some areas and less waving agent in others. Over waving or processing tends to occur in the more porous portions of the hair while underwaving or processing tends to occur in less porous areas. These trends are exactly the inverse of what is desired since the hair which usually needs the waving treatment the most gets the least waving, and visa versa.
Many products today are directed to the special problems and needs of the Black ethnic market. People in the Black ethnic market have, for example, hair characterized by a relatively large number of cystine bonds and relatively high dryness. Conventional permanent waving products have particular limitations applied to this market. Typically, the products result in a hair style that is either very curly and quite greasy or relatively straight and stiff and very dry. These prior products are characterized by the need for frequent, heavy maintenance, e.g., the consumer's application of activators and moisturizers on a daily basis or more than daily basis. None of the prior art compounds are able to produce a Black ethnic hairstyle characterized by thick, full-bodied hair fibers which form loose bouncy curls having good moisture retention.
Another problem that occurs during the hair disulfide bond breaking process is skin irritation caused by the thiol-containing agents. Irritation occurs usually because beauticians frequently use their bare fingers for the wrapping process.
U.S. Pat. No. 4,391,286 (Hsiung et al.) and related U.S. Pat. No. 4,572,220 (Hsiung et al.) both disclose hair conditioning formulations that claim to overcome some of the problems just described. The '286 patent teaches a composition of water having dissolved therein a quaternary nitrogen containing polymer and a water-soluble, disulfide-containing polycarboxylic acid or salt. The '220 patent teaches the same composition as the '286 patent with the addition of a thiol-containing waving agent. The preferred disulfide-containing polycarboxylic acids are formed by the oxidation of two molecules of mercapto-monocarboxylic acid. Examples of these compounds include dithiodiglycolic acid, three-dithiodipropionic acid, cystine, dithiodilactic acid, dithiodisuccinic acid and the like. The preferred quaternary nitrogen containing polymer is a cationic guar where a chloride anion is usually associated with the polymer. The cationic guar is distinguished from other forms or derivatives of guar gum, such as nonionic guar which does not contain quaternary nitrogen compounds. Both formulations disclosed in these two patents are specifically designed and recommended for use on the hair after shampooing and prior to a waving process (i.e., pre-wrap solutions).
Another hair conditioning formulation is disclosed in U.S. Pat. No. 4,588,760 (Jachowicz et al.). This formulation for decreasing hair hygroscopicity and improving settability comprises an aqueous solution of heximinium salt and resorcinol. To facilitate application of this conditioning formulation, it is disclosed that a cosmetically acceptable thickener, such as guar gum, may be incorporated into the formulation.
All of the known waving processes and solutions associated therewith are limited in their flexibility to produce a looser, bouncier, curl while maintaining the moisture of the curls. The present invention provides an improved in hair waving process, eliminating many of the problems associated with prior art processes and solutions.